Chronic pain affects more than 50 million Americans per year, resulting in extraordinary personal and societal costs in diminished quality of life, los productivity and health care consumption. Improved treatments of acute and chronic pain conditions require a thorough understanding of the processes underlying the transmission and perception of painful stimuli. Discovery of the molecular and cellular mechanisms underlying acute and chronic pain is critical to the development of new treatments, particularly in mechanisms regulating the transition from acute to chronic pain. Recent studies from our laboratory have identified an endogenous analgesic mechanism that is present in peripheral sensory neurons conveying pain and is mediated by G protein-coupled receptors (GPCRs) for adenosine diphosphate (ADP). This project will investigate the role of ADP receptors signaling through Gi/o in hyperalgesia resulting from inflammatory injury, the regulation of P2Y signaling by GPCR kinases GRK2 and GRK3 during hyperalgesia, and will explore the hypothesis that these receptors are highly effective in ameliorating hyperalgesia mediated by adenylyl cyclase, a fundamental component of inflammatory pain. Specific Aim 1 will investigate the distribution of GRK2 and GRK3 in dorsal root ganglion (DRG) neurons and their regulation of P2Y signaling in vitro. Specific Aim 2 will determine whether GRK2 and GRK3 are co-regulated in the setting of inflammatory injury, and will examine the impact of altered GRK signaling on P2Y receptor inhibition of adenylyl cyclase using real-time cAMP imaging in vitro. Specific Aim 3 will determine the extent to which changes in the regulation of P2Y signaling contribute to the resolution of inflammatory hyperalgesia in vivo and whether manipulation of these pathways may provide a novel approach to the treatment of inflammatory pain. This proposal will examine the value of Gi/o-coupled P2Y receptors as targets for novel analgesic drugs, and will advance our understanding of fundamental mechanisms regulating GPCR function and nociceptive processing in the peripheral nervous system.